/Engine/Source/Editor/UnrealEd/Public/Kismet2/BlueprintEditorUtils.h
Creates a function graph, but does not add it to the blueprint. If bIsUserCreated is true, the entry/exit nodes will be editable. SignatureFromObject is used to find signature for entry/exit nodes if using an existing signature. The template argument SignatureType should beUClassorUFunction.
template<typename SignatureType> static void CreateFunctionGraph ( [UBlueprint](API\Runtime\Engine\Engine\UBlueprint) * Blueprint, class [UEdGraph](API\Runtime\Engine\EdGraph\UEdGraph) * Graph, bool bIsUserCreated, SignatureType * SignatureFromObject )